Nasa Considering Solar Max Overhaul

April 1, 1985|By James Fisher of The Sentinel Staff

CAPE CANAVERAL — One year after shuttle astronauts snatched the Solar Maximum sun observatory and repaired it in orbit, scientists want to try another mission in 1989 to replace instruments and give the satellite several more years of life.

The mission, now under study, would include installing advanced scientific instruments that could significantly improve the quality of information the satellite is gathering about the sun.

This week a National Aeronautics and Space Administration committee will meet to make a list of recommended new instruments.

A shuttle crew also would load the satellite into the cargo bay and move it to a higher orbit, where it could continue operating into the mid-1990s or later as the sun goes through another highly active phase.

Solar Max, a 5,000-pound satellite orbiting about 300 miles above Earth, was launched in 1980 to study the sun in its solar maximum year, when flares and other solar activity were at their peak. Another peak will occur about 1990 or 1991.

About 10 months after the satellite was launched electronic problems developed. Solar Max could no longer be pointed with precision toward the sun, causing most of its instruments to become useless.

Shuttle astronauts came to the rescue on April 10 last year when they grabbed the slowly spinning satellite with the shuttle's robot arm and pulled Solar Max into the payload bay. It was repaired the next day.

Two spacewalking crewmen replaced the directional control system and made a repair to the electronics box of one scientific instrument. They sent the satellite back to work almost as good as new, with only one experiment not working.

Since then, scientists have been elated.

''The spacecraft Solar Max is beautiful and working well. The instruments are working well,'' said Frank Cepollina, project manager for the repair mission. ''We've gone way past our minimum expectations of performance.''

The instruments were intended to give a complete picture of solar flares (explosive eruptions on the sun) and how they are formed, as well as study sunspots and find out how they are related to magnetic fields on the sun.

Larry Orwig, a scientist monitoring one of the Solar Max instruments, said the satellite is providing valuable data about the sun's less active phase. That will be compared with studies of the sun's peak activity in 1980, when there were up to 30 solar flares a day.

''Scientifically, there's no question the repair was worth doing. Although we're in the declining stage of the solar cycle, there's still a lot of science that can and has been done,'' he said.

Research on solar activity is expected to reveal details of the sun's effect on Earth's weather and climate and electronic communications. Solar flares are suspected of causing garbles in radio communication and electrical surges in power lines.

Even before the repair the Solar Max instruments had produced ''really pioneering breakthroughs'' in solar research, Cepollina said.

But much more information is needed and Solar Max will stop collecting data around 1989 unless NASA agrees to some more in-space tinkering.

The satellite is losing altitude each year and by the end of the decade it will no longer be able to point itself accurately toward the sun, Cepollina said.

Solar Max would need to be moved up to a higher orbit and on the same trip should have upgraded instruments installed. It also may need a battery recharge or replacement of its power control box.

Planners expect that astronauts would remove the entire top section of the satellite, which contains all the instruments, said Brian Dennis, head of the science committee that is considering new instruments.

It would be replaced with a new instrument package that would allow astronauts to change separate instruments at will.

Since the Solar Max instruments were designed in the 1970s ''there have been dramatic improvements in the capability of instruments of this type,'' Dennis said.

A new mission would cost about $50 million, about the same cost as last year's repair mission, Dennis said. However, that is seen as only a ballpark figure, and the exact cost would depend on the type of instruments chosen.

NASA planners said they hope to finalize a mission proposal in two or three months and, if approved, will later face the major hurdle of funding.

''There are always funding battles. This mission has to compete with every other mission on its own merits,'' Cepollina said.

Solar Max cost $70 million to build in the 1970s and a new satellite would have cost $230 million last year, officials said.

Keeping the satellite in space years longer will stretch the value of the investment.

''It's a very cheap sort of science. We are using the resources that are already in orbit,'' Dennis said.